Level 14 and 16 pro-tip, let the slow units spawn until nothing else spawns and kill them with bombs. Do this for the last part and since you kill about 50ish units at once you get that much money doubled ;)
Is there something that should make my allies lose HP by themselves? Sometimes there are no enemies on the screen and they lose a good portion of their health, but only a few troops..
Thanks! We think we're pretty cool too!